Added locustio to tests pip requirements.
Added locustio to tests pip requirements.

Issue #585

pixelated/pixelated-user-agent,pixelated/pixelated-user-agent,pixelated-project/pixelated-user-agent,pixelated/pixelated-user-agent,pixelated-project/pixelated-user-agent,pixelated-project/pixelated-user-agent,pixelated-project/pixelated-user-agent,pixelated/pixelated-user-agent,pixelated-project/pixelated-user-agent,pixelated/pixelated-user-agent